Multi-speed transaxle for a front wheel drive vehicle

ABSTRACT

A front wheel drive transmission is provided having an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes a sun gear member, a planet carrier member, and a ring gear member. The torque transmitting devices include clutches and brakes arranged within a transmission housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/030,261, filed on Feb. 21, 2008, which is hereby incorporated in itsentirety herein by reference.

FIELD

The invention relates generally to a multiple speed transmission havinga plurality of planetary gear sets and a plurality of torquetransmitting devices and more particularly to a transmission configuredfor a front wheel drive vehicle having eight or more speeds, fourplanetary gear sets and a plurality of torque transmitting devices.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission uses a combination of a pluralityof torque transmitting mechanisms, planetary gear arrangements and fixedinterconnections to achieve a plurality of gear ratios. The number andphysical arrangement of the planetary gear sets, generally, are dictatedby packaging, cost and desired speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed transmission.

SUMMARY

In one aspect of the present invention, a transaxle is provided having atransmission input member, a transmission output member, a plurality ofplanetary gear sets, and a plurality of torque-transmitting mechanisms.

In another aspect of the present invention, a housing having a firstwall, a second wall and a third wall extending between the first andsecond walls is provided. The first, second, third and fourth planetarygear sets are disposed within the housing. The first planetary gear setis adjacent the first wall, the second planetary gear set is adjacentsecond wall, the fourth planetary gear set is adjacent the firstplanetary gear set and the third planetary gear set is between thefourth and second planetary gear sets.

In yet another aspect of the present invention, each planetary gear sethas a sun gear member, a ring gear member, and a planet carrier membersupporting a plurality of planet gears each configured to intermesh withboth the sun gear member and the ring gear member. The ring gear memberof the first planetary gear set is permanently coupled to the sun gearmember of the second planetary gear set, the sun gear member of thefirst planetary gear set is permanently coupled to the sun gear memberof the fourth planetary gear set, the ring gear member of the thirdplanetary gear set is permanently coupled to the planet carrier memberof the fourth planetary gear set.

In yet another aspect of the present invention, the output member ispermanently coupled with the carrier members of the second and thirdplanetary gear sets. The input member is permanently coupled with thecarrier member of the first planetary gear set.

In yet another aspect of the present invention, the housing has a firstarea defined radially inward from an outer periphery of the planetarygear sets and axially bounded by the first wall and the first planetarygear set. A second area is defined radially inward from the outerperiphery of the planetary gear sets and axially bounded by the firstand fourth planetary gear sets. A third area is defined radially inwardfrom the outer periphery of the planetary gear sets and axially boundedby the fourth and third planetary gear sets. A fourth area is definedradially inward from the outer periphery of the planetary gear sets andaxially bounded by the second and third planetary gear set. A fifth areais defined radially inward from the outer periphery of the planetarygear sets and axially bounded by the second planetary gear set and thesecond wall. A sixth area is defined radially inward from the third walland radially outward from the outer periphery of the planetary gear setsand axially bounded by the first wall and the second wall.

In yet another aspect of the present invention, the first clutch isdisposed in at least one of the first, second, third and sixth areas andis selectively engageable to interconnect the ring gear member of thefirst planetary gear set with the sun gear member of the third planetarygear set.

In yet another aspect of the present invention, a second clutch isdisposed in at least one of the first, second, third and sixth areas andis selectively engageable to interconnect the planet carrier member ofthe first planetary gear set with the sun gear member of the thirdplanetary gear set.

In yet another aspect of the present invention, a third clutch isdisposed in at least one of the fourth, fifth and sixth areas and isselectively engageable to interconnect the ring gear member of thesecond planetary gear set with the sun gear member of the thirdplanetary gear set.

In yet another aspect of the present invention, a first brake isdisposed in at least one of the first, second, fifth and sixth areas andis selectively engageable to interconnect the sun gear member of thefirst planetary gear set and the sun gear member of the fourth planetarygear set to the housing.

In yet another aspect of the present invention, a second brake isdisposed in at least one of the first, second, fifth and sixth areas andis selectively engageable to interconnect the ring gear member of thefourth planetary gear set to the housing.

In still another aspect of the present invention, the clutches and thebrakes are selectively engageable to establish at least eight forwardspeed ratios and at least one reverse speed ratio between thetransmission input member and the transmission output member.

In still another aspect of the present invention, a power transferassembly has a first and a second transfer gear and a power transfermember. The first transfer gear is rotatably fixed to the engine outputmember and the second transfer gear is rotatably fixed to thetransmission input member. The power transfer member is rotatablycoupled to the first and second transfer gears for transferringrotational energy from the first transfer gear to the second transfergear.

In still another aspect of the present invention, a final driveplanetary gear set has a final drive sun gear coupled to thetransmission output member, a final drive ring gear coupled to thetransmission housing and a final drive carrier member rotatablysupporting a final drive plurality of pinion gears intermeshed with boththe final drive sun gear and the final drive ring gear.

In still another aspect of the present invention, a differential gearset having a differential housing coupled to the final drive carriermember and has a pair of gears rotatably supported in the differentialhousing. One of the pair of the gears is rotatably fixed to one of apair of road wheels and the other of the pair of the gears is rotatablyfixed to the other one of the pair of road wheels.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1A is a schematic diagram of a gear arrangement for a front wheeldrive transmission, according to the principles of the presentinvention;

FIG. 1B is a chart showing the locations of the torque transmittingdevices for the arrangement of planetary gear sets of the transmissionshown in FIG. 1A, in accordance with the embodiments of the presentinvention; and

FIG. 2 is a schematic diagram of a front wheel drive transaxlearrangement incorporating the gear arrangement of the transmission ofFIG. 1A and FIG. 1B, according to the principles of the presentinvention.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

Referring now to FIG. 1A, an embodiment of a front wheel drivemulti-speed or eight speed transmission is generally indicated byreference number 10. The transmission 10 is illustrated as a front wheeldrive or transverse transmission, though various other types oftransmission configurations may be employed. The transmission 10includes a transmission housing 12, an input shaft or member 14, anoutput shaft or member 16 and a gear arrangement 18. The input member 14is continuously connected to an engine (shown in FIG. 2) or to a turbineof a torque converter (not shown). The output member 16 is continuouslyconnected with a final drive unit (not shown) or transfer case (shown inFIG. 2).

The gear arrangement 18 of transmission 10 includes a first planetarygear set 20, a second planetary gear set 22, a third planetary gear set24, and a fourth planetary gear set 26. The planetary gear sets 20, 22,24 and 26 are connected between the input member 14 and the outputmember 16.

In a preferred embodiment of the present invention, the planetary gearset 20 includes a ring gear member 20A, a planet carrier member 20B thatrotatably supports a set of planet or pinion gears 20D (only one ofwhich is shown) and a sun gear member 20C. The ring gear member 20A isconnected for common rotation with a first shaft or intermediate member42 and a second shaft or intermediate member 44. The planet carriermember 20B is connected for common rotation with input shaft or member14 and third shaft or intermediate member 46. The sun gear member 20C isconnected for common rotation with a fourth shaft or intermediate member48. The pinion gears 20D are each configured to intermesh with both thesun gear member 20C and the ring gear member 20A.

The planetary gear set 22 includes a ring gear member 22A, a planetcarrier member 22B that rotatably supports a set of planet or piniongears 22D and a sun gear member 22C. The ring gear member 22A isconnected for common rotation with a fifth shaft or intermediate member50. The planet carrier member 22B is connected for common rotation withoutput shaft or member 16. The sun gear member 22C is connected forcommon rotation with the second shaft or intermediate member 44. Thepinion gears 22D are each configured to intermesh with both the sun gearmember 22C and the ring gear member 22A.

The planetary gear set 24 includes a ring gear member 24A, a planetcarrier member 24B that rotatably supports a set of planet or piniongears 24D and a sun gear member 24C. The ring gear member 24A isconnected for common rotation with a sixth shaft or intermediate member52. The planet carrier member 24B is connected for common rotation withthe output shaft or member 16. The sun gear member 24C is connected forcommon rotation with the seventh shaft or intermediate member 54 and aneighth shaft or intermediate member 56. The pinion gears 24D are eachconfigured to intermesh with both the sun gear member 24C and the ringgear member 24A.

The planetary gear set 26 includes a ring gear member 26A, a carriermember 26B that rotatably supports a set of planet or pinion gears 26Dand a sun gear member 26C. The ring gear member 26A is connected forcommon rotation with a ninth shaft or intermediate member 58. The planetcarrier member 26B is connected for common rotation with the sixth shaftor intermediate member 52. The sun gear member 26C is connected forcommon rotation with the fourth shaft or intermediate member 48. Thepinion gears 26D are each configured to intermesh with both the sun gearmember 26C and the ring gear member 26A.

The transmission 10 also includes a plurality of torque-transmittingmechanisms or devices including a first clutch 66, a second clutch 68, athird clutch 70, a first brake 72 and a second brake 74. The firstclutch 66 is selectively engagable to connect the first shaft orintermediate member 42 to the eighth shaft or intermediate member 56.The second clutch 68 is selectively engagable to connect the third shaftor intermediate member 46 to the eighth shaft or intermediate member 56.The third clutch 70 is selectively engagable to connect the fifth memberor intermediate member 50 to the seventh shaft or intermediate member54. The first brake 72 is selectively engagable to connect the fourthshaft or intermediate member 48 to the transmission housing 12 torestrict rotation of the member 48 relative to the transmission housing12. Finally, the second brake 74 is selectively engagable to connect theninth shaft or intermediate member 58 to the transmission housing 12 torestrict rotation of the member 58 relative to the transmission housing12.

The transmission 10 is capable of transmitting torque from the inputshaft or member 14 to the output shaft or member 16 in at least eightforward torque ratios and one reverse torque ratio. Each of the forwardtorque ratios and the reverse torque ratio are attained by engagement ofone or more of the torque-transmitting mechanisms (i.e. first clutch 66,second clutch 68, third clutch 70, first brake 72 and second brake 74).Those skilled in the art will readily understand that a different speedratio is associated with each torque ratio. Thus, eight forward speedratios may be attained by the transmission 10.

The transmission housing 12 includes a first wall or structural member102, a second wall or structural member 104 and a third wall orstructural member 106. The third wall 106 interconnects the first andsecond walls 102 and 104 to define a space or cavity 110. Input shaft ormember 14 is supported by the first wall 102 by bearings 112. Outputshaft or member 16 is supported by the second wall 104 by bearings 114.The planetary gear sets 20, 22, 24 and 26 and the torque-transmittingmechanisms 66, 68, 70, 72 and 74 are disposed within cavity 110.Further, cavity 110 has a plurality of areas or zones A, B, C, D, E, andF in which the plurality of torque transmitting mechanisms 66, 68, 70,72 and 74 will be specifically positioned or mounted, in accordance withthe preferred embodiments of the present invention.

As shown in FIG. 1A, zone A is defined by the area or space bounded by:the first wall 102, planetary gear set 20, radially inward by areference line “L” which is a longitudinal line that is axially alignedwith the input shaft 14, and radially outward by a reference line “M”which is a longitudinal line that extends adjacent an outer diameter orouter periphery of the planetary gear sets 20, 22, 24 and 26. Whilereference line “M” is illustrated as a straight line throughout theseveral views, it should be appreciated that reference line “M” followsthe outer periphery of the planetary gear sets 20, 22, 24 and 26, andaccordingly may be stepped or non-linear depending on the location ofthe outer periphery of each of the planetary gear sets 20, 22, 24 and26. Zone B is defined by the area bounded by: planetary gear set 20, theplanetary gear set 26, radially outward by reference line “M”, andradially inward by reference line “L”. Zone C is defined by the areabounded by: the planetary gear set 24, the planetary gear set 26,radially outward by reference line “M”, and radially inward by referenceline “L”. Zone D is defined by the area bounded by: the planetary gearset 22, the planetary gear set 24, radially outward by reference line“M”, and radially inward by reference line “L”. Zone E is defined by thearea bounded by: the planetary gear set 22, the second end wall 104,radially outward by reference line “M”, and radially inward by referenceline “L”. Zone F is defined by the area bounded by: the first wall 102,the second wall 104, radially inward by reference line “M” and radiallyoutward by the third wall 106.

In the gear arrangement 18 of transmission 10 shown in FIG. 1A, theplanetary gear set 20 is disposed closest to the first wall 102, theplanetary gear set 22 is disposed closest to the second wall 104, theplanetary gear set 26 is disposed adjacent the planetary gear set 20,and the planetary gear set 24 is disposed between the planetary gearsets 22 and 26. The torque-transmitting mechanisms are intentionallylocated within specific Zones in order to provide advantages in overalltransmission size, packaging efficiency, and reduced manufacturingcomplexity. In the particular example shown in FIG. 1A, the first andsecond clutches 66 and 68 are disposed within Zone A, the first andsecond brakes 72 and 74 are disposed within Zone F and the third clutch70 is disposed within Zone D.

However, the present invention contemplates other embodiments where thetorque-transmitting mechanisms 66, 68, 70, 72 and 74 are disposed in theother Zones. The feasible locations of the torque-transmittingmechanisms 66, 68, 70, 72 and 74 within the Zones are shown in the chartof FIG. 1B. The chart of FIG. 1B lists clutches and brakes in the leftmost column and the available zones to locate the clutch/brake in thetop row. An “X” in the chart indicates that the present inventioncontemplates locating the clutch or brake in the zone listed in the toprow. For example, first brake 72 may be located in zones A, B, E or F,second brake 74 may be located in zones A, B, E or F, first clutch 66may be located in zones A, B, C or F, second clutch 68 may be located inzones A, B, C or F and third clutch 70 may be located in zones D, E orF.

Referring now to FIG. 2, a front wheel drive powertrain 150incorporating a transaxle 154 is illustrated, in accordance with theembodiments of the present invention. Transaxle 154 includes thetransmission 10 having the gear arrangement 18 of FIGS. 1A and 1B.Transaxle 154 is mounted to an engine 156. Engine 156 produces a drivingtorque in an engine output shaft 157 that drives the input shaft 14 oftransmission 10, as described below. Engine 156 is generally an internalcombustion engine, however, the present invention contemplates othertypes of engines such as electric and hybrid engines. Further, transaxle154 includes a transfer chain or belt 158, a drive sprocket or gear 160,a driven sprocket or gear 162, a differential 164, a final driveplanetary gear set 166 and a pair of drive axles 168 and 170 that drivea pair of road wheels 172 and 174, respectively.

Transfer chain or belt 158 engages at a first end 180 the drive sprocketor gear 160 and at a second end 182 the driven sprocket or gear 162. Thedrive sprocket or gear 160 is coupled to engine output shaft or member157. Driven sprocket 162 is rotatably fixed to a drive shaft orrotatable member 159. Drive shaft or rotatable member 159 is coupled tothe input shaft 14 of transmission 10. The output shaft 16 oftransmission 10 is connected to an output sleeve shaft 163. Outputsleeve shaft 163 is coupled to a sun gear of a final drive planetarygear set 166 to achieve the desired gear ratio. A carrier member offinal drive planetary gear set 166 supports a plurality of pinion gearswhich mesh with both the sun gear and a ring gear of final driveplanetary gear set 166. The carrier member of final drive planetary gearset 166 is rotatably coupled to and transfers driving torque to ahousing of the differential 164. Differential 164 transfers the drivingtorque generated by engine 156 to the two drive axles 168 and 170through two sets of bevel gears rotationally supported in thedifferential housing. Drive axles 168 and 170 are rotatably fixed to andindependently driven by the bevel gears of the differential 164 tosupply the driving torque to the vehicle road wheels 172 and 174.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A transaxle coupled to an engine output member, the transaxlecomprising: a transmission input member; a transmission output member; ahousing having a first wall, a second wall, and a third wall extendingbetween the first and second walls; a first, second, third and fourthplanetary gear sets disposed within the housing, wherein the firstplanetary gear set is adjacent the first wall, the second planetary gearset is adjacent second wall, the fourth planetary gear set is adjacentthe first planetary gear set and the third planetary gear set is betweenthe fourth and second planetary gear sets, each planetary gear sethaving a sun gear member, a ring gear member, and a planet carriermember supporting a plurality of planet gears each configured tointermesh with both the sun gear member and the ring gear member, andwherein the ring gear member of the first planetary gear set ispermanently coupled to the sun gear member of the second planetary gearset, the sun gear member of the first planetary gear set is permanentlycoupled to the sun gear member of the fourth planetary gear set, thering gear member of the third planetary gear set is permanently coupledto the planet carrier member of the fourth planetary gear set, theoutput member is permanently coupled with the carrier members of thesecond and third planetary gear sets and the input member is permanentlycoupled with the carrier member of the first planetary gear set, andwherein the housing has a first area defined radially inward from anouter periphery of the planetary gear sets and axially bounded by thefirst wall and the first planetary gear set, a second area definedradially inward from the outer periphery of the planetary gear sets andaxially bounded by the first and fourth planetary gear sets, a thirdarea defined radially inward from the outer periphery of the planetarygear sets and axially bounded by the fourth and third planetary gearsets, a fourth area defined radially inward from the outer periphery ofthe planetary gear sets and axially bounded by the second and thirdplanetary gear set, a fifth area defined radially inward from the outerperiphery of the planetary gear sets and axially bounded by the secondplanetary gear set and the second wall, and a sixth area definedradially inward from the third wall and radially outward from the outerperiphery of the planetary gear sets and axially bounded by the firstwall and the second wall; a first clutch disposed in at least one of thefirst, second, third and sixth areas; a second clutch disposed in atleast one of the first, second, third and sixth areas; a third clutchdisposed in at least one of the fourth, fifth and sixth areas; a firstbrake disposed in at least one of the first, second, fifth and sixthareas; a second brake disposed in at least one of the first, second,fifth and sixth areas, and wherein the clutches and the brakes areselectively engageable to establish at least eight forward speed ratiosand at least one reverse speed ratio between the transmission inputmember and the transmission output member, and a power transfer assemblyhaving a first and a second transfer gear and a power transfer member,wherein the first transfer gear is rotatably fixed to the engine outputmember and the second transfer gear is rotatably fixed to thetransmission input member and wherein the power transfer memberrotatably couples the first and second transfer gears for transferringrotational energy from the first transfer gear to the second transfergear; a final drive planetary gear set having a final drive first membercoupled to the transmission output member, a final drive second membercoupled to the transmission housing and a final drive third member; anda differential gear set having a differential housing coupled to thefinal drive third member and having a pair of gears rotatably supportedin the differential housing, wherein one of the pair of the gears isrotatably fixed to one of a pair of road wheels and the other of thepair of the gears is rotatably fixed to the other one of the pair ofroad wheels.
 2. The transaxle of claim 1 wherein the first clutch isselectively engageable to interconnect at least one of the ring gearmember of the first planetary gear set and the sun gear member of thesecond planetary gear set with the sun gear member of the thirdplanetary gear set and is disposed in the first area, the second clutchis disposed in the first area, the third clutch is disposed in thefourth area, the first brake is disposed in the sixth area and thesecond brake is disposed in the sixth area.
 3. The transaxle of claim 1wherein the first clutch is disposed within the second area.
 4. Thetransaxle of claim 1 wherein the first clutch is disposed within thethird area.
 5. The transaxle of claim 1 wherein the first clutch isdisposed within the sixth area.
 6. The transaxle of claim 1 wherein thesecond clutch is selectively engageable to interconnect the planetcarrier member of the first planetary gear set with the sun gear memberof the third planetary gear set and wherein the second clutch isdisposed within the first area.
 7. The transaxle of claim 1 wherein thesecond clutch is disposed within the second area.
 8. The transaxle ofclaim 1 wherein the second clutch is disposed within the third area. 9.The transaxle of claim 1 wherein the second clutch is disposed withinthe sixth area.
 10. The transaxle of claim 1 wherein the third clutch isselectively engageable to interconnect the ring gear member of thesecond planetary gear set with the sun gear member of the third andwherein the third clutch is disposed within the fourth area.
 11. Thetransaxle of claim 1 wherein the third clutch is disposed within thethird area.
 12. The transaxle of claim 1 wherein the third clutch isdisposed within the sixth area.
 13. The transaxle of claim 1 wherein thefirst brake is selectively engageable to interconnect the sun gearmember of the first planetary gear set and the sun gear member of thefourth planetary gear set to the housing and wherein the first brake isdisposed within the sixth area.
 14. The transaxle of claim 1 wherein thefirst brake is disposed within the fifth area.
 15. The transaxle ofclaim 1 wherein the first brake is disposed within the second area. 16.The transaxle of claim 1 wherein the first brake is disposed within thefirst area.
 17. The transaxle of claim 1 wherein the second brake isselectively engageable to interconnect the ring gear member of thefourth planetary gear set to the housing and wherein the second brake isdisposed within the sixth area.
 18. The transaxle of claim 1 wherein thesecond brake is disposed within the fifth area.
 19. The transaxle ofclaim 1 wherein the second brake is disposed within the second area. 20.The transaxle of claim 1 wherein the second brake is disposed within thefirst area.
 21. A transaxle coupled to an engine output member, thetransaxle comprising: a transmission input member; a transmission outputmember; a housing having a first wall, a second wall, and a third wallextending between the first and second walls; a first, second, third andfourth planetary gear sets disposed within the housing, wherein thefirst planetary gear set is adjacent the first wall, the secondplanetary gear set is adjacent second wall, the fourth planetary gearset is adjacent the first planetary gear set and the third planetarygear set is between the fourth and second planetary gear sets, eachplanetary gear set having a sun gear member, a ring gear member, and aplanet carrier member supporting a plurality of planet gears eachconfigured to intermesh with both the sun gear member and the ring gearmember, and wherein the ring gear member of the first planetary gear setis permanently coupled to the sun gear member of the second planetarygear set, the sun gear member of the first planetary gear set ispermanently coupled to the sun gear member of the fourth planetary gearset, the ring gear member of the third planetary gear set is permanentlycoupled to the planet carrier member of the fourth planetary gear set,the output member is permanently coupled with the carrier members of thesecond and third planetary gear sets and the input member is permanentlycoupled with the carrier member of the first planetary gear set, andwherein the housing has a first area defined radially inward from anouter periphery of the planetary gear sets and axially bounded by thefirst wall and the first planetary gear set, a second area definedradially inward from the outer periphery of the planetary gear sets andaxially bounded by the first and fourth planetary gear sets, a thirdarea defined radially inward from the outer periphery of the planetarygear sets and axially bounded by the fourth and third planetary gearsets, a fourth area defined radially inward from the outer periphery ofthe planetary gear sets and axially bounded by the second and thirdplanetary gear set, a fifth area defined radially inward from the outerperiphery of the planetary gear sets and axially bounded by the secondplanetary gear set and the second wall, and a sixth area definedradially inward from the third wall and radially outward from the outerperiphery of the planetary gear sets and axially bounded by the firstwall and the second wall; a first clutch disposed in at least one of thefirst, second, third and sixth areas and is selectively engageable tointerconnect the ring gear member of the first planetary gear set withthe sun gear member of the third planetary gear set; a second clutchdisposed in at least one of the first, second, third and sixth areas andis selectively engageable to interconnect the planet carrier member ofthe first planetary gear set with the sun gear member of the thirdplanetary gear set; a third clutch disposed in at least one of thefourth, fifth and sixth areas is selectively engageable to interconnectthe ring gear member of the second planetary gear set with the sun gearmember of the third planetary gear set; a first brake disposed in atleast one of the first, second, fifth and sixth areas and is selectivelyengageable to interconnect the sun gear member of the first planetarygear set and the sun gear member of the fourth planetary gear set to thehousing; a second brake disposed in at least one of the first, second,fifth and sixth areas and is selectively engageable to interconnect thering gear member of the fourth planetary gear set to the housing, andwherein the clutches and the brakes are selectively engageable toestablish at least eight forward speed ratios and at least one reversespeed ratio between the transmission input member and the transmissionoutput member, and a power transfer assembly having a first and a secondtransfer gear and a power transfer member, wherein the first transfergear is rotatably fixed to the engine output member and the secondtransfer gear is rotatably fixed to the transmission input member andwherein the power transfer member rotatably couples the first and secondtransfer gears for transferring rotational energy from the firsttransfer gear to the second transfer gear; a final drive planetary gearset having a final drive sun gear coupled to the transmission outputmember, a final drive ring gear coupled to the transmission housing anda final drive carrier member rotatably supporting a final driveplurality of pinion gears intermeshed with both the final drive sun gearand the final drive ring gear; and a differential gear set having adifferential housing coupled to the final drive carrier member andhaving a pair of gears rotatably supported in the differential housing,wherein one of the pair of the gears is rotatably fixed to one of a pairof road wheels and the other of the pair of the gears is rotatably fixedto the other one of the pair of road wheels.
 22. The transaxle of claim21, wherein the power transfer member is a chain or a belt.